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Journal of Biomedical Optics

Comparative study of methods to calibrate the stiffness of a single-beam gradient-force optical tweezers over various laser trapping powers
Author(s): Mohammad Sarshar; Winson Wong; Bahman Anvari
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Paper Abstract

Optical tweezers have become an important instrument in force measurements associated with various physical, biological, and biophysical phenomena. Quantitative use of optical tweezers relies on accurate calibration of the stiffness of the optical trap. Using the same optical tweezers platform operating at 1064 nm and beads with two different diameters, we present a comparative study of viscous drag force, equipartition theorem, Boltzmann statistics, and power spectral density (PSD) as methods in calibrating the stiffness of a single beam gradient force optical trap at trapping laser powers in the range of 0.05 to 1.38 W at the focal plane. The equipartition theorem and Boltzmann statistic methods demonstrate a linear stiffness with trapping laser powers up to 355 mW, when used in conjunction with video position sensing means. The PSD of a trapped particle’s Brownian motion or measurements of the particle displacement against known viscous drag forces can be reliably used for stiffness calibration of an optical trap over a greater range of trapping laser powers. Viscous drag stiffness calibration method produces results relevant to applications where trapped particle undergoes large displacements, and at a given position sensing resolution, can be used for stiffness calibration at higher trapping laser powers than the PSD method.

Paper Details

Date Published: 6 November 2014
PDF: 13 pages
J. Biomed. Opt. 19(11) 115001 doi: 10.1117/1.JBO.19.11.115001
Published in: Journal of Biomedical Optics Volume 19, Issue 11
Show Author Affiliations
Mohammad Sarshar, Univ. of California, Riverside (United States)
Winson Wong, Univ. of California, Riverside (United States)
Bahman Anvari, Univ. of California, Riverside (United States)

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